Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$32.88	7.573%	$35.37	$35.37	$35.35	$35.40
Purchase #2	$226.39	10.545%	$250.2628	$250.26	$250.25	$250.30
Purchase #3	$37.42	8.375%	$40.5539	$40.55	$40.55	$40.60
Purchase #4	$194.83	11.710%	$217.6446	$217.64	$217.65	$217.60
Purchase #5	$138.58	5.288%	$145.9081	$145.91	$145.90	$145.90
Purchase #6	$239.28	6.556%	$254.9672	$254.97	$254.95	$255.00
Purchase #7	$172.39	13.731%	$196.0609	$196.06	$196.05	$196.10
7 purchase totals =	$1,041.77		$1,140.7675	$1,140.76	$1,140.70	$1,140.90